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What is a data dictionary?

Learn the basics about data dictionaries. What are they, what do they look like, and what could they include?  

Having a conversation

A data dictionary is a conversation between you, the publisher of the data, and others who may want to use that data. The level of detail you need to include in your data dictionaries entirely depends on what your data contains, who wants to use it, and what you think you need to tell them. 

[Video] What are data dictionaries?

Basic data dictionary

A basic data dictionary may only describe:

  • the dataset
  • each variable or column (name and description)
  • the variable type 
  • any code used as values in each column (for example, 0 for ‘male’ and 1 for ‘female’).

For instance, Waka Kotahi publishes a data dictionary for their New Zealand Vehicle Fleet Open Data. This data dictionary, provided in a machine readable CSV format, describes what you need to know in order to use the data.

The New Zealand Vehicle Fleet Open Data 
Motor vehicle registry open data dictionary [CSV 9 KB]
Data formats for open data

Basic data dictionary example

Name   Type   Description   Units   Codes   Values
Industry_class   Text   The class of industry a vehicle is associated with       1|2|3|4|...|99  


Power_rating   Integer   The power rating of the vehicle   kW        

Comprehensive data dictionary

A comprehensive data dictionary may go further, also describing:

  • the source data
  • the sampling methods
  • any data transformation
  • the software code used to prepare the data
  • the standards used
  • the reliability of the data
  • any quality concerns.   

For instance, Stats NZ publishes a data dictionary for their Consumers Price Index dataset. This data dictionary describes everything one needs to know to find and use the data with complete confidence. 

Stats NZ Consumers Price Index data dictionary
The Consumers Price Index

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Content last reviewed 11 January 2021.